Wheel hub drives are frequently used for the travelling drive of industrial trucks. These are a combination of a wheel bearing and a gear system for the transformation of the driving torques and rotation numbers. Wheel hub drives are used in industrial trucks for unsteered as well as for steered wheels. The gear system transmits the driving torque from the drive motor to the driving wheel. The wheel bearing serves to support the vertical forces of the wheels. The space for construction is normally extremely limited, so that a compact construction is required.
In the state of the art, a series of wheel hub drives has become known. From EP 1 167 140 B1, the entire contents of which is incorporated herein by reference, or DE 102 58 913 A1, the entire contents of which is incorporated herein by reference, wheel hub drives have become known in which two taper roller bearings in O-arrangement form the wheel bearing and the drive gear system, realised as a planetary gear system, is disposed coaxially to the wheel's central axis. The outer diameter of the taper roller bearings is largely identical with the partial circle diameter of a hollow wheel of the planetary gear system. A wheel hub drive of similar construction, in which the drive gear system is radially accommodated in the wheel bearing and into which a brake as well as a drive motor is built in, is described in DE 100 61 221 A1.
DE 196 33 071 C2, the entire contents of which is incorporated herein by reference, discloses an one step planetary gear system for a wheel hub drive, in which the planet carrier serves for accommodating the wheel bearing, which consists of a roller bearing on the torque leading side and a roller bearing on the not torque leading side of the planet carrier laterally besides the planetary step. In order to reach the required gear ratio of the drive gear system, the planetary gear system is supplemented by a parallel shaft gear system, so that the drive motor is positioned hypoid to the wheel's central axis.
In DE 199 11 458 A1, the entire contents of which is incorporated herein by reference, a wheel hub drive of a wheel steered by an electric motor is disclosed, in which wheel bearing and drive gear system are disposed side by side. A fifth wheel for the wheel drive unit is rotatably mounted in the vehicle frame via a four point bearing, the steering gear system, realised as a wolfrom gear system, being accommodated radially inside the four point bearing. In the mentioned document, an arrangement is also disclosed by which a fifth wheel bearing, formed by two roller bearings, and the steering gear system realised as a planetary gear system are disposed one above the other, coaxially to the driving axis.
In DE 101 32 319 A1, the entire contents of which is incorporated herein by reference, DE 100 62 315 A1, the entire contents of which is incorporated herein by reference, and DE 103 34 939 A1, the entire contents of which is incorporated herein by reference, wheel hub drives for steered wheels are described, wherein drive motor or drive gear system are disposed radially inside at least one roller bearing of the wheel bearing, and the fifth wheel is rotatably mounted in the vehicle frame with the aid of a four point bearing.
The present invention is based on the objective to provide a wheel hub drive for industrial trucks, in which the unit consisting of drive gear system and wheel bearing is realised as to be particularly compact. An arrangement with outside diameter as small as possible and limited width is to be provided in particular, which transmits a maximum torque to the driving wheel.